Navigating the Dancefloor: The Elegance of Named Routes

TL;DR Hey, you can name routes now! You can also create links to them! It also works in templates! Okay read on!

Paths, Paths, Paths

When working with a large web application or service that includes numerous routes that serve multiple purposes, one significant need is to generate paths the user will use to navigate between the routes.

In templates for pages, you need to create links and forms that point to other routes. Take this contrived example:

# In your template
<!-- part of the menu -->
[% FOREACH user IN users %]
<a href="/view/user/[% user_id %]?track=[% track_code %]">User [% %]>/a><br/>
[% END %]

Let's say your application is mounted (using Plack::Builder or using some web server configuration on top of /admin. Well, those paths won't work anymore. Now they need to be /admin/view/user/..., right?

Generating Paths

We can fix this using uri_for:

<a href="[% request.uri_for("/view/user/$user_id?track=$track_code") %]">
User [% %]

This will take into account the possible mounting. Also, it can take care of the query parameter for the tracking code.

<a href="[% request.uri_for("/view/users/$user_id", { track => $track_code }) %]">
User [% %]

While it's longer, it's definitely more readable and less error-prone.

Hardcode Me Not

The two problems that remain are needing to remember the path for each route and to hardcode it in the template or any code that generates paths for the user.

We can fix both of those with the new uri_for_route().

Name that Route

Begin by providing a name for your routes:

get 'view_user' => '/view/user/:id' => sub {...};

By prefixing the path with another string, we provide a name for this route which we can then use to generate a URI for its path in the template or in any code.

Enter uri_for_route

Now let's use the route's name with uri_for_route:

<a href="[% request.uri_for_route("view_user", { id => $user_id }) %]">
User [% %]

Oh, and we can also include the tracking code as a query parameter:

<a href="[% request.uri_for_route("view_user", { id => $user_id }, { track => $track_code }) %]">
User [% %]

Naming All Options

uri_for_route has a lot of arguments. It's worthwhile exploring them:

  1. Route name

    The name of the route as you have given it. You can provide a name to all routes except HEAD. This means GET, POST, PUT, PATCH, and DELETE.

  2. Route arguments

    These will be the arguments to the route path. We support named arguments, typed named arguments, splat, and megasplat:

    # Named arguments
    post 'req_form' => '/upload/request/:id' => sub {...};
    $path = uri_for_route( 'req_form', { 'id' => 4 } );
    # $path = /upload/request/4
    # Typed named arguments
    post 'req_form' => '/upload/request/:id[Num]' => sub {...};
    $path = uri_for_route( 'req_form', { 'id' => 4 } );
    # $path = /upload/request/4
    # Splat and Megasplat
    post 'req_form' => '/upload/request/*/*/**' => sub {...};
    $path = uri_for_route( 'req_form', [ 'foo', 'bar', [ 'baz', 'quux' ] ] );
    # $path = /upload/request/foo/baz/baz/quux
    # And a mix of these
    post 'req_form' => '/upload/request/:id/*/*/**' => sub {...};
    $path = uri_for_route(
            'id'    => 4,
            'splat' => [ 'foo', 'bar', [ 'baz', 'quux' ] ],
    # $path = /upload/request/4/foo/baz/baz/quux

    (Notice that when you're mixing these, the splat-like arguments will be under the splat key which shouldn't be used in route arguments.)

  3. Query parameters
    get 'view_user' => '/view/user/:id' => sub {...};
    $path = uri_for_route(
        'view_user',        # Route name
        { 'id'  => 4     }, # Route arguments
        { 'ext' => 'str' }, # Query parameters
    ); # $path = /view/user/4?ext=str
  4. URI escape control

    Lastly, we escape all query parameters by default since a user is likely to be using them. You don't want accidental HTML and JS code to be there.

    However, the last argument allows you to disable this ability:

    get 'view_user' => '/view/user/:id' => sub {...};
    $path = uri_for_route(
        'view_user',                    # Route name
        { 'id'  => 4 },                 # Route arguments
        { 'ext' => '<javascript>...' }, # Query parameters
        1,                              # Disable escaping
    ); # $path = /view/user/4?ext=<javascript>...

    (We still suggest you leaving this as is, so escaping will occur.)


This article has been written by Sawyer X for the Perl Dancer Advent Calendar 2023.